kremkau chapter 6 key terms Flashcards
aliasing
improper Doppler shift information from a pulsed spectral Doppler or color Doppler instrument when the true Doppler shift exceeds 1/2 the PRF
anechoic
echo free
comet tail
a series of closely spaced reverberation echoes
cross talk
leakage of strong signals in one direction channel of a Doppler receiver into the other channel; can produce the spectral Doppler mirror image artifact
enhancement
increase in echo amplitude from reflectors that lie behind a weekly attenuating structure.
hypoechoic
having relatively weak echoes. opposite of hyperechoic.
mirror image
an artifactual grey scale, color flow, or Doppler signal appearing on the opposite side of a strong reflector.
nyquist limit
the Doppler shift frequency above which aliasing occurs; 1/2 half of the PRF
range ambiguity
an artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were received from the first pulse.
reverberation
multiple reflection
shadowing
reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure.
slice thickness
thickness of the scanned tissue volume perpendicular to the scan plane; aka section thickness
speckle
the granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in echoes.
speed error
propagation speed that is different from the assumed value.
